Rotary bender with hybrid saddle

ABSTRACT

A bending apparatus consisting of a rocker rotating in a hybrid constructed saddle. The saddle is preferably made of a steel casing with a low friction liner disposed therein.

This application is based on, and claims priority to, provisionalapplication Ser. No. 60/938,735, having a filing date of May 18, 2007,entitled Rotary Bender with Hybrid Saddle.

FIELD OF THE INVENTION

The invention relates generally to rotary bending tools, such as thoseused in die presses.

BACKGROUND OF THE INVENTION

Embodiments of the invention concern rotary bending tools, which aretypically used to form bends in a sheet metal workpiece by wrappingaround an edge of an anvil die. In particular, the invention relates tobending tools of the type that have a rocker rotationally mounted in acylindrical seat in a saddle. In an illustrative bending tool to whichthe invention pertains, the rocker has a lengthwise V-shaped recess thatwraps the edge of a sheet metal blank around an anvil die edge as thesaddle is driven down in a press. As it descends, the rotation of therocker wraps the sheet material around the lower die edge.

Such devices are used in high volume production of formed steel panelsand thus are subject to considerable wear. Rockers for long lengthrotary bending tools have been constructed of very high strength alloyswhich are hardened prior to machining, necessitating costly posthardening machining to very close tolerances. The durability and ease ofmaintainability of a rotary bending apparatus is greatly dependent onthe lubricity of the rocker and saddle interface. Therefore,sophisticated lubricating systems are necessary for smooth movementbetween the rocker and the saddle. Additionally, the surface of thecylindrical seat in the saddle must be extremely smooth. This can beproblematic because it is difficult to hone the internal diameter of theseat to a smooth enough surface. Accordingly, there is a need for anapparatus that has low friction between the rocker and saddle, yet canwithstand high volume production applications, is cost effective, and islow maintenance.

SUMMARY OF THE INVENTION

Advantageously, embodiments of the invention provide a rotary bendingtool saddle that increases the flexibility of selecting appropriatelymatched rocker and liner materials for the best fit to the applicationrequirements.

Embodiments of the invention include a rotary bending tool having asaddle having an elongated member formed with an at least partiallycylindrical open recess extending lengthwise along the saddle; and arocker having an elongated member with at least a partially cylindricalouter surface fit to the at least partially cylindrical portion of thesaddle recess, such that the saddle recess allows relative rotation ofthe rocker therein; wherein the saddle comprises a high strength housingwith a liner disposed therein, the liner formed of a low frictionmaterial.

The liner may be constructed of various materials such as, bronze,bearing bronze, aluminum bronze, polymers, filament wound composites andgraphite composites. The rocker may also be formed of various materialsincluding graphite composites.

DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read with the accompanying drawings.

FIG. 1 is a cross-sectional view of a rotary bending tool according toan illustrative embodiment of the invention.

FIG. 2 depicts a perspective view of rotary bending tool according to afurther illustrative embodiment of the invention.

FIGS. 3A-C depict a cross-sectional view of a rotary bending toolaccording to an illustrative embodiment of the invention.

FIG. 4 depicts an exploded view of rotary bending tool according to afurther illustrative embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention include a unique saddle usedin a rotary bending tool. The saddle has a housing, preferablycomprising a durable, stiff, low cost material that is easilymanufactured, such as steel. The saddle housing has a low frictionliner, such as a bearing bronze to reduce friction between the rockerand saddle. The inner diameter of the saddle can also be honed to a verysmooth surface prior to being inserted into the saddle housing, reducingor eliminating the need to grind the saddle recess.

FIG. 1 depicts a rotary bending tool 10 according to an illustrativeembodiment of the invention. Saddle 14 has a housing 30 with a partiallycylindrical recess to enable saddle 14 to partially encircle rocker 12.A liner 40 is disposed within saddle recess 18. Liner 40 is formed of amaterial that reduces friction between saddle 14 and rocker 12 ascompared to the friction that would occur between saddle 14 and rocker12 without the liner during operation of the rotary bending tool. Rocker12 is typically assembled within saddle 14 by being slid endwise intosaddle recess 18. Rocker 12 has a V-shaped recess 16 extendinglengthwise along rocker 12. V-shaped recess 16 is positioned toinitially face away from the saddle recess.

A series of pins 20 are each received in one of a series of holes 22 insaddle 14. A compression spring 26 is associated with each pin 20.Rocker 12 is retained in position by pins 20 inserted through respectiveholes 22 in saddle 14 and received in respective pockets 24 in rocker12. The tapered end pins 20 are urged towards rocker 12 by compressionsprings 26 compressed by set screws 28 installed in threaded sections ofholes 22. Compressed springs 26 allow pins 20 to be forced back asrocker 12 is rotated by contact of a recess edge 32 with workpiece P.The rotary bending tool 10 can be installed in a die press by means ofcap screws (not shown) and mates with a lower die D having an elongatedforming contour C around which a sheet metal workpiece P is wrapped, asdescribed in the above referenced patent, which process is well known inthe art, and will not be further described here.

FIG. 1 depicts pins 20 entering saddle 14 horizontally. Pins may alsohave other orientations, such as shown in FIG. 2. The angled orientationshown in FIG. 2 may be desirable, for example when space or clearance isnot sufficient for the horizontal arrangement.

FIGS. 3A-C depict the rotary bending tool 200 of FIG. 2 bending a metalworkpiece P around an anvil A according to an illustrative embodiment ofthe invention. As spring 202 is compressed, rocker 212 rotates in saddle214. As rocker recess edge 232 rotates, it breaks the plane of thesaddle lower bottom surface, thereby bending workpiece P, which wasinitially parallel to the saddle bottom surface.

Depending on the materials of the liner and rocker, and the formation ofthose parts, liner 40 can reduce friction to the extent additionallubrication is not necessary. Under certain conditions, however, one ormore supplementary lubricating mechanisms may be desirable.

One such lubrication mechanism includes use of lubricating plugs in thesaddle. In the illustrative embodiment of the invention shown in FIGS. 1and 4, two linear series of lubricant-impregnated graphite plugs 34 areinserted in pockets in saddle recess 18 in the region above rocker 12 asviewed when the rotary bending tool is positioned for use. The lubricantcan be an oil or a synthetic lubricating material. Although the term“pocket” generally refers to a structure having a closed end, as usedherein, “pockets” in the saddle include openings that may extend throughthe outer surface of the saddle housing. The ends of the graphite plugs34 are preferably machined to an arcuate shape matching the curvature ofrocker 12 and saddle recess 18. This arrangement has been found toadequately lubricate rocker 12 even when the forming operations arecontinued over many cycles. Materials other than graphite may be used,for example other soft metals or polymers. A desirable feature of theplug material is that it can be impregnated with a lubricant.Non-impregnated plugs can be used provided they impart a lubricatingresidue on the rocker.

Instead of, or in addition to, lubricating plugs, the liner material maybe impregnated with a lubricant, such as oil. In an illustrativeembodiment of the invention, the liner may be sintered bronze, which hasintrinsic porosity and is easily impregnated with lubricant.

It was noted above that a suitable material for the saddle housing issteel. Other high strength materials are also suitable, but cost willoften be a factor. A high strength alloy steel is particularly desirablein many applications. Other illustrative materials include cast iron,extruded aluminum and molded structural polymers.

The saddle liner may be constructed of various low friction materials.Bronze, which is typically 60% copper and 40% tin, has very littlemetal-on-metal friction, and therefore, is quite suitable for a linermaterial. Bronze having other elements incorporated therein, such asbearing bronze, aluminum bronze and phosphor bronze, manganese bronze,and silicon bronze are also suitable. Additional illustrative examplesof liner materials include graphite, graphite composites, polymers, andfilament wound composites.

Filament winding is a well known process for the production ofcomposites. In a typical filament wound composite a continuous filamentof reinforcing material, such as glass fiber, is coated with a resin.The key characteristic of a suitable filament wound composite is lowfriction.

Graphite composites may include for example graphite or Teflon® orvarious combinations, such as DuPont's Delrin® or DuPont's Vespel®.Delrin® comprises an acetal resin (acetal polyoxymethylene (POM)) withhomopolymer and copolymer grades available. Delrin® products may containvarious other components such as Kevlar® or Teflon® and silicone oil.Stronger composites, such as HyComp® thermoplastics are also suitable.These may include materials made by HyComp® such as WearComp® andFibreComp®, which are comprised of carbon fiber with a polyimide binder.Generally, “composites” as used herein will have a fiber reinforcementcomponent and a polymer binder or matrix material. The WearComp®,WearComp®200, and FibreComp® materials use a thermoset polyimide binder.These materials are typically compression molded. Thermoplastics, whichcan be injection molded, can also be used. These may include for examplePEEK, manufactured by Victrex® and Torlon® manufactured by Amoco.

Polymer-containing materials can usually be extruded to the saddleshape, or the liner, thereby eliminating machining except for the springhole. The aforementioned composites can be used with a steel rockerwithout a liner, or they can be used for the liner with a steel rocker.Also, they may be used to form the rocker, which can be implemented witha steel saddle. It may also be possible to have both the rocker and thesaddle or liner made of the same composite.

Advantageously, when machining is eliminated, heat treating, grinding,and honing may also be eliminated. There may be minimal smoothing of theparts, but significantly less than with machined parts. Additionally,tool marking will be reduced on the workpiece, friction will be reduced,and it can be easier for the user to alter the components when needed,for example for fine-tuning the rocker angle.

The liner is a partial cylinder, which will generally be formed byremoving a section or quadrant of the cylinder. With most materials, theinternal diameter of the liner will shrink when the section is removed.A sizing rod can be used to expand the inner diameter to the desiredsize.

The liner may comprise a plurality of individual lengths instead ofbeing one continuous cylinder. This can be advantageous to produce longlengths that are consistent in dimensions.

The saddle liner may be attached to the saddle housing by variousmechanisms, including for example pins 48, bolts, or adhesive.

The saddle liner wall thickness is preferably 8%-10% of the rockerdiameter. If the wall is too thin, there is an insufficient amount ofreserve oil in the graphite plugs that can be contained in the saddlewall, requiring more frequent replacement. Additionally, if the linerwall is too thin, it can be difficult to attach pins and bolts to theapparatus.

The rocker may be formed of a graphite composite, such as DuPont'sDelrin® or DuPont's Vespel®. Another illustrative rocker material ishigh strength alloy steel. Softer rocker materials having low contactfriction, such as the DuPont polymers mentioned, are desirable whenbending parts for which appearance may be critical, such as prepaintedor polished stainless steel or aluminum. The softer rocker will minimizeunwanted marking of the part. It has been found that having a rocker ofthe same material as the liner can optimize reduction of wear andfriction. In a particular embodiment of the invention, Delrin® or anequivalent is used for both the rocker and liner. It is also noted thatparticular Derlin® or Vespel compositions work better with certainmetals such as aluminum or steel, so rocker material should be matchedappropriately with liner material to achieve a desired balance offriction, strength, and effect in the workpiece. Reduction of frictionreduces the bending load, which also reduces the tool's marks on thepart being bent. If the life of the rotary bending tool components isthe primary objective and slight burnishing on the part is acceptable, asteel rocker can be used with a Derlin® liner. Advantageously, having aliner in the saddle increases the flexibility and of selective rockerand liner materials for the best fit to the application requirements.

The housing dimensions are generally dictated by the space required forthe rocker, return spring and the mounting holes. The outer dimensionsof the rotary bending tool are generally dictated by the available spacein the apparatus in which it is incorporated.

The invention also includes a method of fabricating the embodiments ofthe rotary bending tools described herein. The methods include forming asaddle housing, forming a saddle liner, and inserting the saddle linerin the saddle housing. The saddle housing and liner are formed of thematerials described herein or their equivalents. A further illustrativemethod includes forming the liner of a plurality of lengths. Theformation and insertion of other components as provided above comprisefurther illustrative embodiments and steps of the inventive methods.This includes for example, formation and insertion of various types offriction reducing plugs.

Embodiments of the invention also include a method of bending aworkpiece using any of the embodiments of the rotary bending tooldescribed herein.

Embodiments of the invention also include a die press having any of theembodiments of the rotary bending tool described herein incorporatedinto it.

While the invention has been described by illustrative embodiments,additional advantages and modifications will occur to those skilled inthe art. Therefore, the invention in its broader aspects is not limitedto specific details shown and described herein. Modifications, forexample to materials used in the rotary bending tool components and thetype of tool incorporating the inventive technology, may be made withoutdeparting from the spirit and scope of the invention. Accordingly, it isintended that the invention not be limited to the specific illustrativeembodiments, but be interpreted within the full spirit and scope of theappended claims and their equivalents.

1. A rotary bending tool comprising: a saddle having an elongated memberformed with an at least partially cylindrical open recess extendinglengthwise along the saddle; and a rocker having an elongated memberwith at least a partially cylindrical outer surface fit to the at leastpartially cylindrical portion of the saddle recess, such that the saddlerecess allows relative rotation of the rocker therein; wherein thesaddle comprises a high strength housing with a liner disposed therein,the liner formed of a low friction material.
 2. The rotary bending toolof claim 1 wherein the liner is selected from the group consisting ofbearing bronze, aluminum bronze and phosphor bronze, manganese bronze,and silicon bronze.
 3. The rotary bending tool of claim 1 wherein theliner is phosphor bronze.
 4. The rotary bending tool of claim 1 whereinthe liner is aluminum bronze.
 5. The rotary bending tool of claim 1wherein the liner comprises s a polymer.
 6. The rotary bending tool ofclaim 1 wherein the liner is a filament wound composite.
 7. The rotarybending tool of claim 1 wherein the liner is a graphite composite. 8.The rotary bending tool of claim 1 wherein the rocker is a graphitecomposite.
 9. The rotary bending tool of claim 1 wherein the linercomprises a plurality of individual lengths.
 10. The rotary bending toolof claim 1 further comprising: one or more openings within the saddle,the openings open to the recess therein; and friction reducing plug(s)mounted in the one or more openings, the plugs each having an endengaging the rocker cylindrical surface thereby lubricating the rockercylindrical surface.
 11. The rotary bending tool of claim 10 wherein theplugs are an oil-impregnated metal.
 12. The rotary bending tool of claim10 wherein the plugs are an oil-impregnated graphite.
 13. The rotarybending tool of claim 10 wherein the plugs are an oil-impregnatedpolymer.
 14. A method of fabricating a rotary bending tool of the typehaving: a saddle having an elongated member formed with an at leastpartially cylindrical open recess extending lengthwise along the saddle;and a rocker having an elongated member with at least a partiallycylindrical outer surface fit to the at least partially cylindricalportion of the saddle recess, such that the saddle recess allowsrelative rotation of the rocker therein; the method comprising: forminga saddle housing; former a saddle liner; and inserting the saddle linerwithin the saddle housing.
 15. The method of claim 14 comprising formingthe liner of a material selected from the group consisting of bearingbronze, aluminum bronze and phosphor bronze, manganese bronze, andsilicon bronze.
 16. The method of claim 14 comprising forming the linerof bearing bronze.
 17. The method of claim 14 comprising forming theliner of aluminum bronze.
 18. The method of claim 14 comprising formingthe liner of a polymer containing material.
 19. The method of claim 14comprising forming the liner of a filament wound composite.
 20. Themethod of claim 14 comprising forming the liner of a graphite composite.21. The method of claim 14 comprising forming the rocker of a graphitecomposite.
 22. The method of claim 14 comprising forming the liner of aplurality of individual lengths.
 23. The method of claim 14 comprisingforming the liner by extruding a polymer-containing material.
 24. Themethod of claim 14 comprising: forming one or more openings within thesaddle, the openings open to the recess therein; and inserting frictionreducing plug(s) in the one or more openings, the plugs each having anend engaging the rocker cylindrical surface thereby lubricating therocker cylindrical surface.
 25. The method of claim 24 comprising:wherein the plugs are an oil-impregnated metal.
 26. The method of claim25 wherein the plugs are an oil-impregnated graphite.
 27. A method ofbending a workpiece comprising: placing a workpiece in a rotary bendingtool according to claim
 1. 28. A die press having a rotary bending toolaccording to claim
 1. 29. A rotary bending tool comprising: a saddlehaving an elongated member formed with an at least partially cylindricalopen recess extending lengthwise along the saddle; and a rocker havingan elongated member with at least a partially cylindrical outer surfacefit to the at least partially cylindrical portion of the saddle recess,such that the saddle recess allows relative rotation of the rockertherein; wherein the saddle comprises a composite having a polymerbinder, and wherein
 30. A method of fabricating a rotary bending tool ofthe type having: a saddle having an elongated member formed with an atleast partially cylindrical open recess extending lengthwise along thesaddle; and a rocker having an elongated member with at least apartially cylindrical outer surface fit to the at least partiallycylindrical portion of the saddle recess, such that the saddle recessallows relative rotation of the rocker therein; the method comprising:forming the saddle by extruding a high strength composite.